1. Field of the Invention
This invention relates to an absorbent article comprising a odour control material and in particular to an article for absorbing fluids, for example, bodily fluids, the said article comprising an odour control material which is a buffer.
Absorbent articles are designed to be worn by humans to absorb bodily fluids, such as urine, menstrual fluid and perspiration, etc. Examples of absorbent articles include sanitary napkins, pantiliners, disposable diapers, incontinence pads, tampons and the like.
2. Description of the Related Art Including Information Disclosed Under 37 C.F.R. 1.97 and 1.98.
In use, the absorbent articles are known to acquire a variety of compounds, for example volatile fatty acids (e.g. isovaleric acid), ammonia, amines (e.g. triethylamine), fatty acids, sulphur containing compounds (e.g. mercaptans, sulphides), alcohols, ketones and aldehydes (e.g. furaldehyde) which release unpleasant odours. These compounds may be present in the bodily fluid or may be produced by fermentation once the bodily fluid is absorbed into the pad. In addition menstrual fluid which contains microorganisms can also generate malodorous by products. Unpleasant odours which emanate from absorbent pads when in use may make the wearer feel self conscious.
A number of compounds, mixtures, compositions and the like are known to combat some of the unpleasant odours referred to above many of which are based on absorbents such as activated carbon, clay and zeolites.
U.S. Pat. No. 3,939,838 discloses an article for treating menstrual fluid having the function of effectively removing odour that is released from menstrual fluid. The odour controls exemplified are active carbon, active silica, active alumina, ion exchange resin and chlorophyll.
EP-A-0509409 discloses an absorbent article which contains an anhydrous non-buffer odour control mixture which includes at least basic and pH neutral odour absorbing particles, and optionally acidic odour absorbing particles. It is disclosed that for feminine articles very small amounts of acid, less than about 10%, preferably less than about 5% and most preferably less than about 1% of the total weight of the deodorizing mixture is required. The basic odour absorbing particle can be used between about 25 to 99%, preferably 75 to 95%, of the total deodorizing mixture and the pH neutral odour absorbing particles may be included in about 1 to 25 and preferably 15 to 20% of the total weight of the deodorizing mixture.
U.S. Pat. No. 3,995,636 discloses a catamenial device, in particular a tampon, which comprises a segment of a rapidly re-expandable hydrophilic polymeric foam held in compression by a constraining means. The constraining means comprises a coating material that includes a mixture of citric acid and sodium bicarbonate. It is disclosed that the coating composition restores the slightly acidic environment in the vaginal area and thus prevents undue accumulation of noxious odour and irritation which results from enzymic reduction of uric acid, urea, amino acids and the like constituting menstrual discharge, to ammonia and volatile amines.
U.S. Pat. No. 5,122,407 discloses an absorbent pad cover having lasting odour control effect and in particular discloses a non-woven web of fibrous material, a fluorocarbon polymer composition adhered to the fibres throughout the web, an odour absorbing reagent bound to the web by the fluorocarbon composition and rendered hydrophoric thereby and a plurality of apertures defined through the web. Suggested odour absorbing reagents are activated carbon, ABSCENTS (ABSCENTS is a registered Trade Mark) (synthetic zeolite), sodium bicarbonate and carbonates, bicarbonates, phosphates, biphosphates, sulfates and bisulphates of alkali and alkaline earth metals; ascorbic acid, boric acid, citric acid and maleic acid.
U.S. Pat. No. 5,130,352 discloses mouldable filled polyethylene compositions containing particulate lignocellulosic fillers. Boric acid and/or borax is added to the composition to suppress odour during manufacture and processing of the compositions.
Some previously used absorbents are not particularly efficient in removing unpleasant odours. Other absorbents, whilst efficient at removing unpleasant odours, may have other disadvantages and, for example, the black colour of carbon black is aesthetically unappealing in an absorbent pad.